-rw-r--r--
symbolic notation
| Read (r) | Write (w) | Execute (x) | # | |
|---|---|---|---|---|
| Owner | 6 | |||
| Group | 4 | |||
| Others | 4 |
What this means
β’ Owner can read, write
β’ Group can read
β’ Others can read
Common Presets
chmod stands for 'change mode' β the Unix command used to set file or directory permissions. Permissions control who can read, write, or execute a file: the owner, the group, or others.
755 means: owner has read+write+execute (7), group has read+execute (5), others have read+execute (5). It is the standard permission for publicly accessible directories and executable files.
644 means: owner has read+write (6), group has read only (4), others has read only (4). It is the standard permission for regular files like HTML, CSS, or config files.
Each group of 3 characters represents owner, group, and others. 'r' = read, 'w' = write, 'x' = execute, '-' = no permission. So rwxr-xr-x means owner has full access, group and others have read+execute.
777 grants read, write, and execute to everyone (owner, group, and others). It is dangerous because any user on the system β or a compromised web process β can modify or execute the file. Avoid 777 in production; use 755 for directories and 644 for files.
The execute (x) bit allows a file to be run as a program, or allows a directory to be entered (cd into). Directories should almost always have execute permission β without it, you cannot list or access their contents even if you have read permission.
The sticky bit (chmod +t or octal 1xxx) on a directory prevents users from deleting files they do not own. The /tmp directory uses 1777 β everyone can write, but only the file owner can delete their files. Useful for shared directories.
Unix file permissions control who can read, write, and execute files and directories. Misconfigurations are a common source of security vulnerabilities. This calculator makes it easy to build and understand permission values without memorizing the octal number system.
Enter an octal value or use checkboxes
Type a 3-digit octal permission (like 755 or 644) directly, or click the read/write/execute checkboxes for owner, group, and others to build the value visually.
Read the symbolic notation
The tool shows the equivalent symbolic notation (rwxr-xr-x) alongside the octal value. Both representations are used in Linux β octal in chmod commands, symbolic in ls -l output.
Check the plain-language explanation
The tool explains in plain English what each permission level means β 'Owner can read, write, and execute. Group and others can read and execute.' This catches misconfiguration before it causes problems.
Use a common preset
Select a common preset (755, 644, 700, 777) to start from a known-good configuration. Use presets as a reference and adjust from there.
Set web server file permissions
Web server files typically use 644 (readable by everyone, writable only by owner) and directories use 755. Misconfigured permissions expose writable files to potential attackers or prevent the web server from reading its own files.
Secure SSH keys and credentials
SSH private keys must be 600 (readable only by owner) or SSH will refuse to use them. Use this calculator to confirm the correct permission value before running chmod.
Debug permission denied errors
When a script or application gets a 'Permission denied' error, convert the current permission value and check which permission is missing for the process's user or group.
Unix and Linux file permissions control which users can read, write, and execute a file or directory. Permissions are defined for three classes β owner, group, and others β and expressed in two equivalent ways: symbolic notation (rwxr-xr--) and octal notation (754). The octal representation assigns a digit to each class where read = 4, write = 2, execute = 1, and the digit is the sum of the enabled bits.
Chmod (change mode) is the command used to set these permissions. Developers and system administrators need to set permissions correctly for web server document roots, deployment scripts, SSH keys (which require 600 or 700), and executable binaries. This calculator lets you toggle individual permission bits visually and see the corresponding octal number and chmod command β or enter an octal value and see exactly which permissions it grants to each user class.